Organic light-emitting diode display panel

ABSTRACT

An organic light-emitting diode display panel includes a substrate and a light-emitting pixel array disposed on the substrate, and the light-emitting pixel array includes a plurality of light-emitting pixels. Each of the plurality of light-emitting pixels comprises a convex structure layer, a light-emitting element, a planarization layer and a microlens structure which are sequentially stacked on the substrate. The convex structure layer comprises at least one convex structure which is convex in a direction facing away from the substrate and at least one convex surface where each of the at least one convex structure is in contact with the light-emitting element. The microlens structure and convex structure are aligned each other that their vertical projections on the substrate overlap with a vertical projection of the light-emitting element on the substrate.

CROSS-REFERENCES TO RELATED APPLICATION

This application claims to the priority of Chinese patent applicationNo. 202010628374. 3 filed on Jul. 1, 2020, which is incorporated hereinby reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the field of display technologies and,in particular, to an organic light-emitting diode display panel.

BACKGROUND

In recent years, organic light-emitting diode display (OLED hereinafter)panels have gradually become the mainstream of mobile terminal screensand display screens. An OLED panel includes a plurality of sub-pixelsarranged in an array, where each sub-pixel includes a pixel drivingcircuit and a light-emitting element electrically connected to the pixeldriving circuit.

As part of the large-angle light in the light emitted from the OLEDpanel cannot reach human vision system, a large power consumptionproblem of the OLED panel caused by light waste may occur. In order toensure that the large-angle light emitted from the OLED panel isconverged into the viewing angle of an observer, in the related art, amicro convex lens is configured above each OLED pixel, and light photonsemitted from the light-emitting element in the corresponding pixel areconverged into a parallel or an approximately parallel emitting lightbeam through the micro convex lens, thus ensuring that the output lightphotons are efficiently collected by the human vision system in arelative long distance without being diffused and lost midway.

However, when a convex lens is configured above an OLED pixel, lightemitted from a light-emitting surface having an area about the samedimension as the area of the convex lens cannot be focused into aparallel light beam or an approximately parallel light beam through theconvex lens, and still a considerable part of light is emitted at alarge angle and cannot reach the human vision system, resulting in aloss of more light.

SUMMARY

Embodiments of the present disclosure provide an OLED panel to increasethe weight of parallel light in the light emitted from a microlensstructure, so that the display brightness of the OLED panel isincreased.

An OLED panel is provided in the embodiments of the present disclosureand includes a substrate and a light-emitting pixel array located on thesubstrate and including a plurality of light-emitting pixels.

Each of the plurality of light-emitting pixels includes a convexstructure layer, a light-emitting element, a planarization layer and amicrolens structure which are sequentially stacked on the substrate.

The convex structure layer includes at least one convex structure whichis convex in a direction facing away from the substrate and at least oneconvex surface where each of the at least one convex structure is incontact with the light-emitting element.

The microlens structure and the convex structure are aligned each otherthat their vertical projections on the substrate overlap with a verticalprojection of the light-emitting element on the substrate.

According to the OLED panel provided in the embodiments of the presentdisclosure, the light-emitting pixel includes the convex structurelayer, the light-emitting element, the planarization layer and themicrolens structure which are sequentially stacked on the substrate, themicrolens structure the convex structure are aligned each other thattheir vertical projections on the substrate overlap with the verticalprojection of the light-emitting element on the substrate. The convexstructure is disposed on one side of the light-emitting element facingtowards the substrate, so that through coupling of the convex structureand the microlens structure, the parallel light component among thelight emitted from the microlens structure is increased, and the displaybrightness of the OLED panel is increased.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a cross-sectional view of an OLED panel in a related artaccording to embodiments of the present disclosure;

FIG. 2 shows a cross-sectional view of an OLED panel according toembodiments of the present disclosure;

FIG. 3 shows a cross-sectional view of another OLED panel according toembodiments of the present disclosure;

FIG. 4 shows a cross-sectional view of another OLED panel according toembodiments of the present disclosure;

FIG. 5 plots a function relationship between a convex surface and asurface of the lens according to embodiments of the present disclosure;

FIG. 6 plots a relative relationship in height between surfaces of aconvex surface and a surface of the lens according to embodiments of thepresent disclosure;

FIG. 7 shows a cross-sectional view of a convex structure and microlensstructure according to embodiments of the present disclosure;

FIG. 8 shows a perspective view of an ellipsoid surface;

FIG. 9 plots a simulation example of a convex surface according toembodiments of the present disclosure.

DETAILED DESCRIPTION

Hereinafter the present disclosure is further described in detail inconjunction with the drawings and embodiments. It is to be understoodthat the embodiments set forth below are intended to illustrate and notto limit the present disclosure. Additionally, it is to be noted thatfor ease of description, only part, not all, of the structures relatedto the present disclosure are illustrated in the drawings.

Illustrated in FIG. 1 is a cross-sectional view of an OLED panel in therelated art. As shown in FIG. 1, a microlens structure 20′ is disposedabove each light-emitting pixel 10′, and light photons emitted from thelight-emitting element 30′ in the corresponding light-emitting pixel 10′converge into a parallel or a substantially parallel light beam throughthe microlens structure 20′, thereby ensuring that the output lightphotons are efficiently collected by the human vision system in arelatively long distance without being diffused and lost midway.However, in fact, since the area of the light-emitting element 30′ is insimilar dimension as the microlens diameter and no longer a valid pointsource, only a part of the light photons emitted from the light-emittingelement 30′ can form a parallel or approximately parallel light beamthrough the microlens structure 20′. As shown by the solid line in FIG.1, still a significant portion of the light photons are emitted into thespace beyond a viewing angle of the observer, causing either darkdisplay image or extra power consumption.

Aiming to solve the above-mentioned problems, an OLED panel is providedin the embodiments of the present disclosure. The OLED panel includes asubstrate and an array of light-emitting pixels. The light-emittingpixel includes a convex structure layer, a light-emitting element, aplanarization layer and a microlens structure which are sequentiallystacked on the substrate. The convex structure layer includes one convexstructure. The microlens structure and the convex structure are alignedeach other that their vertical projections on the substrate overlap withthe vertical projection of the light-emitting element on the substrate.Curvature of the microlens and curvature of the convex structure areconformally matching each other in such a way that all normal lighttraces from the light emitting surface will be diffracted and convergedinto a substantially collimated light beam after the microlens. By suchan arrangement, the majority of light photons emitted from thelight-emitting element can be efficiently collected by human visionsystem which is distanced from the OLED panel.

Based on the above basic concept of the present disclosure, variousembodiments of the present disclosure will be described clearly andcompletely in conjunction with drawings of the present disclosure. Allother embodiments or simple replacement or varieties from theembodiments described hereinafter by those of ordinary in the artwithout creative work are within the scope of the present disclosure.

FIG. 2 depicts a cross sectional view of an OLED panel according toembodiments of the present disclosure. As shown in FIG. 2, the OLEDpanel includes a substrate 10 and a light-emitting pixel array disposedon the substrate 10, and the light-emitting pixel array includes aplurality of light-emitting pixels 20. The light-emitting pixel 20includes a convex structure layer 21, a light-emitting element 22, aplanarization layer 23 and a microlens structure 24 which aresequentially stacked on the substrate 10. The convex structure layer 21includes at least one convex structure 210 which is convex in adirection facing away from the substrate 10 and at least one convexsurface 220 where the convex structure 210 is in contact with thelight-emitting element 22. The microlens structure 24 and the convexstructure 210 are aligned each other that their vertical projections onthe substrate 10 overlap with the vertical projection of thelight-emitting element 22 on the substrate 10.

In FIG. 2, P is the focal point of the microlens structure 24, and aconfined area of the light-emitting element inside the cone volumeformed by the bottom edge of the microlens structure 24 and the focalpoint P is Al. As shown in FIG. 2, the convex structure 210 is disposedbetween the light-emitting element 22 and the substrate 10, with itssurface curvature being conformal to the curvature of the microlens.Assume the light-emitting element is Lambert surface, that the mainlight trace, which referring to the light emitted in normal angle fromthe surface of the light-emitting element, has the greatest intensity.Diffracted by the microlens structure 24, all main light traces from thelight emitting element within the cone volume will be converted into acollimated light beam formed by substantially parallel light traces.With less diffusion in output light beam, the brightness of OLED panelare increased. In addition, since the effective light emitting area on acurved light-emitting element is larger than a light-emitting element ona flat surface, the overall light output from OLED is increasedaccordingly.

According to the OLED panel provided in the embodiments of the presentdisclosure, the light-emitting pixel includes the convex structurelayer, the light-emitting element, the planarization layer and themicrolens structure which are sequentially stacked on the substrate. Themicrolens structure and the convex structure are aligned each other thattheir vertical projections on the substrate overlap with the verticalprojection of the light-emitting element on the substrate. Throughcoupling of the convex structure and the microlens structure, theparallel light component among the light emitted from the microlensstructure can be increased, so that the display brightness of the OLEDpanel is increased.

In one embodiment, still referring to FIG. 2, the center of gravity axisL2 that passes through the center of gravity of the convex structure 210coincides with the optical axis L1 of the microlens structure 24.

As shown in FIG. 2, L1 represents the optical axis of the microlensstructure 24, L2 represents the gravity axis of the convex structure210, C represents the center of gravity of the convex structure 210, Prepresents the focal point of the microlens structure 24, and theoptical axis L1 of the microlens structure 24 passes through the point Cof the convex structure 210 and coincides with the center of gravityaxis L2 of the convex structure 210. As shown in FIG. 2, the thick solidline A1 represents the portion of light-emitting element inside aconfined area of the cone volume formed by the bottom edge of themicrolens structure 24 and the focal point P of the microlens structure24. Diffracted by the microlens structure 24, the light photons emittedfrom this portion of the light-emitting element will converge into asubstantially parallel beam after the microlens structure 24, so thatthe light-emitting element 22 inside in the cone volume is a plane lightsource positioned at the lens focal surface of the light-emittingelement. The gravity axis L2 of the convex structure 210 is set tocoincide with the optical axis L1 of the microlens structure 24, so thatthe area of a plane light source positioned at the lens focal surface ofthe light-emitting element inside the cone volume formed by the bottomedge of the microlens structure 24 and the focal point P of themicrolens structure 24 may be ensured to be maximum, the light outputfrom the light-emitting element 22 is increased, and the large-angleemitting light is reduced. By such an arrangement, the majority of lightphotons emitted from the light-emitting element can be efficientlycollected by human eyes which is distanced from the OLED panel.

In one embodiment, still referring to FIG. 2, a ratio of the area of thelight-emitting element 22 inside the cone volume formed by the bottomedge of the microlens structure 24 and the focal point P of themicrolens structure 24 to the area of the light-emitting element 22 isgreater than 50%.

The larger the area of the light-emitting element inside the cone volumeformed by the bottom edge of the microlens structure 24 and the focalpoint P of the microlens structure, the larger the area of the planelight source positioned at the lens focal surface where parallel lightcan be provided, and the smaller the loss of large-angle light. Througha research, the applicant finds that when the ratio of the area of thelight-emitting element 22 inside the cone volume to the area of thelight-emitting element 22 is greater than 50%, that is, when thelight-emitting element 22 has more than half of the area located in thecone volume formed by the bottom edge of the microlens structure 24 andthe focal point P of the microlens structure, the parallelism of thelight beams emitted from the light-emitting element 22 through themicrolens structure 24 can be significantly improved, and thechromaticity of the OLED panel is improved.

In one embodiment, still referring to FIG. 2, the focal point P of themicrolens structure 24 is disposed on the side of the convex surface 220facing towards the substrate 10.

The above configuration ensures that a sufficient area of thelight-emitting element is within the cone volume formed by the bottomedge of the microlens structure 24 and the focal point P of themicrolens structure 24 to improve the parallelism of the light beamsemitted from the light-emitting element 22 through the microlensstructure 24. For example, the focal point P of the microlens structureis disposed inside the convex structure 210 or even on the side of theconvex structure 210 facing away from the light-emitting element 22 toobtain a larger plane light source positioned at the lens focal surface.As can be seen from FIG. 2, a simple way to achieve this purpose is toreduce the thickness of the planarization layer 23 so that the focalpoint P of the microlens structure 24 moves downwards, bringing a largerarea of the light-emitting element 22 into the cone volume.

In one embodiment, still referring to FIG. 2, the light-emitting element22 includes a first electrode 221, a light-emitting functional layer222, and a second electrode 223 sequentially stacked on the convexsurface 220, and the first electrode 221 includes a reflective layercapable of reflecting light.

The OLED panel includes a top emission mode display panel and a bottomemission mode display panel. When the OLED panel is in the top emissionmode, and the first electrode 221 is configured to include thereflective layer capable of reflecting light, a part of the lightemitted from the light-emitting element 22 is reflected to the microlensstructure 24 through the reflective layer on the surface of the firstelectrode 221, which improves the light utilization rate of the OLEDpanel.

Further, as shown in FIG. 3, the light-emitting element includes a firstelectrode 221, a light-emitting functional layer 222, and a secondelectrode 223 which are stacked sequentially on the convex surface,where the first electrode 221 is a transparent electrode; and the OLEDpanel further includes a reflective layer 25 disposed between the convexstructure 210 and the substrate 10.

As shown in FIG. 3, the reflective layer 25 may be configured directlyon one side of the convex structure 210 facing towards the substrate 10,the reflective layer 25 is disposed between the convex structure 210 andthe substrate 10, and when light emitted from the light-emitting element22 partially reaches the non-light-emitting side of the OLED panel, thelight emitted from the light-emitting element 22 is reflected to themicrolens structure 24 through the reflective layer 25 on the substrate10, thereby improving the light utilization rate of the OLED panel.

In one embodiment, on the basis of the above embodiment, FIG. 4 shows across-sectional view of another OLED panel according to embodiments ofthe present disclosure. As shown in FIG. 4, the convex surface 220satisfies that incident light parallel to the optical axis L1 of themicrolens structure 24 is vertically incident on the convex surface 220after the microlens structure 24. Consider a light trace is reversiblein an optical system, the design of optical system of the OLED panel canbe conducted by using incident light rather than emitted light. This issolely for the sake of simplicity hereinafter and are not supposed tovary the results.

As shown in FIG. 4, light beams in parallel with the optical axis L1 ofthe microlens structure 24 are incident on the surface of the microlensstructure 24 and finally impinging on the surface of the light-emittingelement 22 after being focused by the microlens structure 24. Thesurface curvature of the convex structure 210 can be made in a shape toallow the light beams incident on the surface of the convex structure inan essentially normal angle.

The main light refers to light beams emitted from the light-emittingelement 22 of the OLED panel in the direction of a normal perpendicularto the tangent plane of the curved surface of the light-emitting element22. According to the reversibility of the light trace, the main lightemitted from the light-emitting element 22 disposed on the convexstructure 210 will be a form of almost parallel light beams afterpassing through the microlens structure 24, thereby ensuring that thelight emitted from the light-emitting element 22 can be emitted to a farposition and maintain a relatively large photon density, i.e., arelatively small divergence angle, and thus improving the chromaticityof the OLED panel.

It is to be noted that FIG. 4 exemplarily illustrates a light path ofambient light incident on the microlens structure 24 and thenperpendicularly incident on the surface of the light-emitting element22. According to the principle of the reversibility of a light path,when the light-emitting element 22 of the OLED panel emits light, thelight emitted in a tangential direction perpendicular to the surface ofthe light-emitting element 22 forms an approximately parallel light beamto the ambient environment through the microlens structure 24. Theoptical path thereof is opposite to the optical path of the ambientlight incident on the microlens structure 24 and will not be describedagain.

Further, the shape of the convex structure 210 enables the main lightemitted from the light-emitting element 22 covered thereon to form anapproximately parallel light beam through the microlens structure 24.The shape of the curved surface of the microlens structure 24 and theshape of the curved surface of the convex structure 210 or the functionrelationship of the curved surfaces which satisfy the above-mentionedlight beam propagation path are all within the scope of the presentdisclosure.

A functional relationship of the curved surfaces of the convex structure210 and the microlens structure 24 are describes as follows.

In one embodiment, a surface of the lens of the microlens structure 24is a rotationally symmetric curved surface around the optical axis ofthe microlens structure 24 and is represented by a function y=ƒ(x). Theconvex surface 220 is a rotationally symmetric curved surface around acenter of gravity axis of the convex structure 210 and is represented bya function z=Q(x). Where the Z axis represents the center of gravityaxis of the convex structure 210 or the optical axis of the microlensstructure 24, x represents a vertical distance from any point on thesurface of the lens or the convex surface to the Z axis. The functionsf(x) and Q(x) satisfy:

$\begin{matrix}{{{Q(x)} = {{GMT} + {\int_{0}^{x}{\left\lbrack {{f^{\prime}(x)} + \frac{s(x)}{\sqrt{1 - {s^{2}(x)}}}} \right\rbrack{dx}}}}},{and}} & (1)\end{matrix}$ $\begin{matrix}{{s(x)} = {\frac{n1}{n2} \cdot {\frac{f^{\prime}(x)}{\sqrt{1 + \left( {f^{\prime}(x)} \right)^{2}}}.}}} & (2)\end{matrix}$

Where ƒ′(x) represents a first-order differential of ƒ(x), GMT is themaximum thickness of the convex structure, n2 denotes the refractiveindex of the microlens structure 24, and n1 denotes the refractive indexof the medium space outside the microlens structure 24 and on the sidefacing away from the convex structure 210.

As shown in FIG. 5, it is assumed that: the surface of the lens of themicrolens structure 24 is the rotationally symmetric curved surfacearound the optical axis of the microlens structure 24 and is representedby the function z=ƒ(x), the convex surface 220 is the rotationallysymmetric curved surface around the center of gravity axis of the convexstructure 210 and is represented by the function z=Q(x). When a lightbeam parallel to the optical axis L1 of the microlens structure 24 isincident on the curved surface of the microlens structure 24, therefractive index of the medium space outside the microlens structure andon the side facing away from the convex structure is n1, and therefractive index of the microlens structure 24 is n2. The angle ofincidence θ1 and the angle of refraction θ2 of the light beam satisfy:

$\begin{matrix}{{{\theta 1} = {{\alpha 1} = {\arctan\left\lbrack {- {f^{\prime}(x)}} \right\rbrack}}},{and}} & (1)\end{matrix}$ $\begin{matrix}{{\theta 2} = {{\arcsin\left\lbrack {\frac{n1}{n2}\sin({\theta 1})} \right\rbrack}.}} & (2)\end{matrix}$

When the light beam is incident on the curved surface of the microlensstructure 24 and is refracted and then incident on the convex surface220, the angle of incidence θ1 and the angle of refraction θ2 of thelight beam satisfy:θ1−θ2=α2=arctan[−Q′(x)].  (3)

It can be deduced from the above three equations that:

$\begin{matrix}{{Q(x)} = {{Q(0)} + {\int_{0}^{x}{\left\lbrack {{f^{\prime}(x)} + \frac{s(x)}{\sqrt{1 - {s^{2}(x)}}}} \right\rbrack{{dx}.}}}}} & (4)\end{matrix}$

Where s(x) may satisfy

$\begin{matrix}{{s(x)} = {\frac{n1}{n2} \cdot {\frac{f^{\prime}(x)}{\sqrt{1 + \left( {f^{\prime}(x)} \right)^{2}}}.}}} & \end{matrix}$

ƒ′(x) is the first-order differential of ƒ(x)

As can be seen from Equation (4), the expression of the convex surface220 of the convex structure 210 can be obtained by substituting theinitial values of z=ƒ(x) and z=Q(x).

The initial value Q(0) of the convex surface 220 can be solved anddetermined in a following method. As shown in FIG. 6, a special lighttrace, represented by a function LR (r), which is the most peripherylight trace diffracted by the microlens, strikes normally on the surfaceof the convex structure 210. According to Equation (4) and a triangularrelationship illustrated in FIG. 6, it can be derived that:

$\begin{matrix}{{Q^{\prime}(x)} = {\frac{- 1}{\tan\left( \theta_{2} \right)} = {{f^{\prime}(x)} + {\frac{s(x)}{\sqrt{1 - {s^{2}(x)}}}.}}}} & (5)\end{matrix}$

By solving Equation (5), the coordinate of the intersection point ofcurve Q(x) and the light trace LR(x), denoted by x₀, can be obtained.Through solving the formular Q(x₀)=LR(x₀), (6) andLR(x₀)=h₀−tan(θ₂)·(R₀−x₀) (7),

the coordinate of the summit of the convex structure 210 is obtained. InEquation (7), R₀ denotes the radius of the microlens structure, and h₀denotes a height from the focal point of the microlens to the surface ofthe microlens.

In the above embodiment, the curved surface of the microlens structure24 and the convex surface 220 of the convex structure 210 are both idealrotationally symmetric surfaces. However, in actual production, due tomanufacturing process variations, the curvatures of the microlensstructure 24 and the convex structure 210 may vary within a certainrange, for instance varying within positive and negative 15%,nevertheless they are still within the scope of the present disclosure.

In another embodiment, the convex structure 210 is made of a transparentmaterial, and the refractive index of the convex structure 210 isgreater than or equal to the refractive index of the light-emittingelement 22.

Since a first part of the light beams emitted from the light-emittingelement 22 of the OLED panel output toward the direction of themicrolens structure 24, and a second part of the light beams outputtoward the direction of the convex structure 210, when the second partof the light beam reaches the reflective layer 25 through the convexstructure 210 made of the transparent material, the second part of thelight beam is reflected by the reflective layer 25. The refractive indexof the convex structure 210 is set to be greater than or equal to therefractive index of the light-emitting element 22, so that the lightbeams incident on the convex structure 210 can be automaticallyconverged into light beams with a relatively small angle, and the lightbeams passing through the convex structure 210 after being reflected bythe reflective layer 25 are prevented from being emitted at a relativelylarge divergence angle, thereby ensuring that the reflected light isfocused near the optical axis L1 of the microlens structure 24.

It is to be noted that the convex structure 210 is made of a transparentmaterial, and may be considered transparent to visible light or to thespectral band of the light-emitting pixel where the convex structure 210is located.

In another embodiment, the convex structure 210 contains pigmentparticles, and the color of the pigment particle may be the same as thelight-emitting color of the light-emitting pixel where the convexstructure 210 is located, thereby improving the chromaticity of the OLEDpanel.

Further, the pigment particle may be doped in the microlens structure 24as well to add a function of color filtering to the microlens. By suchan arrangement, the color filter film and associated manufactureprocesses can be deleted, resulting in a significant cost saving.

In the embodiments of the present disclosure, the convex surface and/orthe surface of the lens may be in different curved surface shapesaccording to actual design requirements. For example, as shown in FIG.2, the convex surface and/or the surface of the lens may include aportion of a spherical surface. In another example, as shown in FIG. 7,the convex surface and/or the surface of the lens may include a portionof cylindrical surface. As further shown in FIG. 8, the convex surfaceand/or the surface of the lens may include a part of an ellipsoidsurface.

As shown in FIG. 2, when the focal point P of the microlens structure 24is disposed on the side, facing towards the convex structure 210, of theconvex surface where the convex structure 210 and the light-emittingelement 22 are in contact, for example, the focal point of the microlensstructure 24 is point P, the area of the a plane light source positionedat the lens focal surface of the light-emitting element satisfiesA₁=2πr₀ ² (1−cos α₁).

FIG. 2 exemplarily illustrates that the area of the light-emittingelement inside the cone volume formed by the bottom edge of themicrolens structure 24 and the focal point P of the microlens structureis calculated as A1 by taking the convex surface and the surface of thelens as parts of a spherical surface. When the convex surface and/or thesurface of the lens include a portion of cylindrical surface or aportion of an ellipsoid surface, the area of the light-emitting elementinside the cone volume may be calculated as A1 by taking the convexsurface and the surface of the lens as parts of a spherical surfaceaccording to a surface calculation formula of the cylinder or a surfacecalculation formula of an ellipsoid.

Further, the convex surface and/or the surface of the lens include aportion of cylindrical surface, a part of a spherical surface, or a partof an ellipsoid surface, which may be regarded as a portion of standardcylindrical surface, a standard spherical surface, or a standardellipsoid surface in a broad sense, and may also refer to a portion ofapproximate cylindrical surface, an approximate spherical surface, or anapproximate ellipsoid surface.

Optionally, the convex surface includes a portion of an ellipsoidsurface, the long axis of the ellipsoid surface coincides with theoptical axis of the microlens structure 24, and a short axis of theellipsoid surface is less than the diameter of the microlens structure24.

FIG. 9 plots a simulation example according to embodiments of thepresent disclosure. Referring to FIG. 9, the surface of the microlensstructure 24 is configured to be a hemispherical surface, n1 is therefractive index outside of the microlens structure 24 and n1=1, and n2is the refractive index of the microlens structure 24 and n2=1.5. Aconvex surface illustrated by the curve 200 in FIG. 9 is obtainedaccording to Equations (1) to (7). According to the assumption based onwhich the equations (1) to (7) are configured, an incident light beam inparallel with the optical axis of the microlens structure 24 willimpinging vertically on the surface of the convex structure 210. For thepurpose of comparison, a hemispherical surface curve 300 is illustratedat the same position of the curve 200, which suggests an ideal shape ofthe surface of the convex structure 210 is not exactly a semispherical,but rather an ellipsoid surface of a standing football. The long axis ofthe ellipsoid surface coincides with the optical axis of the microlensstructure, the short axis of the ellipsoid curved surface is thereforeperpendicular to the optical axis of the microlens structure. Inaddition, as indicated in FIG. 9, the short axis is less than or equalto the diameter of the microlens structure. As illustrated in FIG. 9, alight beam 400 defines a boundary of the light beam focused by themicrolens structure. An intercept of the light beam 400 and the surfaceof the convex structure defines a starting point of a flat region. Sincethis flat region will not make an important contribution to the outputparallel light beam, the light-emitting element should be disposed onthe surface of the convex structure as much as possible, while othercomponents, such as a pixel definition layer and other circuitcomponents, should be disposed in this region. Due to variations in theactual manufacturing process, the curvatures of the microlens structureand the light-emitting element may not be exact as the curvature givenby the simulation results. Nevertheless, the above simulation resultsprovide a useful guidelines for device design and process parameteradjustment, and any dimension variations and misalignment of componentassembly to some extent from the ideal mathematic model disclosed hereinare still within the scope of disclosures.

The above detailed descriptions of the embodiments of the presentinvention set forth preferred modes contemplated by the inventor forcarrying out the present invention at the time of filing thisapplication, and are provided by way of examples and not as limitations.Accordingly, various modifications and variations obvious to a person ofordinary skill in the art to which it pertains are deemed to lie withinthe scope and spirit of the present invention as set forth in thefollowing claims.

What is claimed is:
 1. An organic light-emitting diode display (OLED)panel, comprising: a substrate; and a light-emitting pixel arraydisposed on the substrate and comprising a plurality of light-emittingpixels; wherein each of the plurality of light-emitting pixels comprisesa convex structure layer, a light-emitting element, a planarizationlayer and a microlens structure which are sequentially stacked on thesubstrate; wherein the convex structure layer comprises at least oneconvex structure which is convex in a direction facing away from thesubstrate and at least one convex surface where the at least one convexstructure is in contact with the light-emitting element; wherein themicrolens structure and the at least one convex structure are alignedwith each other such that their vertical projections on the substrateoverlap with a vertical projection of the light-emitting element on thesubstrate; and wherein each of the at least one convex surface satisfiesthat: light emitted from the light-emitting element and perpendicular tothe convex surface is converted into parallel light that is parallel toan optical axis of the microlens structure after interaction with themicrolens structure.
 2. The OLED panel according to claim 1, wherein acenter of gravity axis passing through a center of each of the at leastone convex structure coincides with the optical axis of the microlensstructure.
 3. The OLED panel according to claim 1, wherein a ratio of anarea of the light-emitting element inside a cone volume formed by abottom edge of the microlens structure and a focal point of themicrolens structure to an area of the light-emitting element is greaterthan 50%.
 4. The OLED panel according to claim 1, wherein a focal pointof the microlens structure is disposed on one side of the at least oneconvex surface facing towards the substrate.
 5. The OLED panel accordingto claim 1, wherein the light-emitting element comprises a firstelectrode, a light-emitting functional layer, and a second electrodewhich are stacked sequentially on the at least one convex surface,wherein the first electrode comprises a reflective layer capable ofreflecting light.
 6. The OLED panel according to claim 1, wherein asurface of a lens of the microlens structure is a rotationally symmetriccurved surface around the optical axis of the microlens structure and isrepresented by a function z=ƒ(x), and each of the at least one convexsurface is a rotationally symmetric curved surface around a center ofgravity axis of one of the at least one convex structure and isrepresented by a function z=Q x); wherein a Z axis represents the centerof the gravity axis of each of the at least one convex structure or theoptical axis of the microlens structure, x denotes a vertical distancefrom any point on the surface of the lens or the each of the at leastone convex surface to the Z axis, and the functions ƒ(x) and Q(x)satisfy: $\begin{matrix}{{{{Q(x)} = {{GMT} + {\int_{0}^{x}{\left\lbrack {{f^{\prime}(x)} + \frac{s(x)}{\sqrt{1 - {s^{2}(x)}}}} \right\rbrack{dx}}}}};}{and}{{{s(x)} = {\frac{n1}{n2} \cdot \frac{f^{\prime}(x)}{\sqrt{1 + \left( {f^{\prime}(x)} \right)^{2}}}}};}} & \end{matrix}$ wherein ƒ′(x) represents a first-order differential ofƒ(x), GMT is a maximum thickness of the each of the at least one convexstructure, n2 denotes a refractive index of the microlens structure, andn1 denotes a refractive index of a medium space outside the microlensstructure and on one side facing away from the each of the at least oneconvex structure.
 7. The OLED panel according to claim 6, wherein theconvex surface and/or the surface of the lens comprise a portion ofcylindrical surface.
 8. The OLED panel according to claim 6, wherein theconvex surface and/or the surface of the lens comprise a portion of aspherical surface or a portion of an ellipsoid surface.
 9. The OLEDpanel according to claim 8, wherein the convex surface comprises aportion of the ellipsoid surface, a long axis of the ellipsoid surfacecoincides with the optical axis of the microlens structure, and a shortaxis of the ellipsoid surface is less than a diameter of the microlensstructure.
 10. The OLED panel according to claim 1, wherein thelight-emitting element comprises a first electrode, a light-emittingfunctional layer, and a second electrode which are stacked sequentiallyon each of the at least one convex surface, wherein the first electrodeis a transparent electrode, and the OLED panel further comprises areflective layer disposed between each of the at least one convexstructure and the substrate.
 11. The OLED panel according to claim 10,wherein each of the at least one convex structure is made of atransparent material, and a refractive index of the each of the at leastone convex structure is greater than or equal to a refractive index ofthe light-emitting element.
 12. The OLED panel according to claim 10,wherein each of the at least one convex structure is doped with apigment particle, and a color of the pigment particle is same as alight-emitting color of a light-emitting pixel where the each of the atleast one convex structure is located.
 13. The OLED panel according toclaim 1, wherein the microlens structure is doped with a pigmentparticle, and a color of the pigment particle is same as alight-emitting color of a light-emitting pixel where the microlensstructure is located.